Integumentary System Outline



Integumentary System Outline Chapter 5 AP&P Girard 2007

I. Integumentary System

A. Skin

1. Skin is a coat

a. Waterproof

b. Stretchable (2.2 m2) (~11 lbs)

c. Washable

d. Auto-repairing (Cuts, tears, & burns)

e. Lasts a lifetime

B. Hair (Keratinized protein secreted by cells)

C. Nails (Hard keratinized protein)

II. Functions

A. Prevents dehydration

B. Prevents bacterial & viral infection (chemical & physical barrier)

1. Most substances cannot penetrate; exceptions are:

a. Vitamins A,D,E,K

b. Oxygen & Carbon dioxide (in limited amounts)

c. Organic solvents (paint thinner, acetone) which dissolve cell lipids

d. Oleoresins of certain plants (e.g. Poison Ivy, Oak, Sumac, etc…)

e. Salts of heavy metals (e.g. Lead, Mercury, Arsenic, etc…)

C. Regulates body temperature

D. Vitamin D synthesis (Needed to absorb calcium in the digestive tract)

E. Blood reservoir (Blood can be shunted to other organs in need e.g. skeletal muscles)

F. Excretion – Water, salt, ammonia, urea, and uric acid are excreted in sweat

III. Epidermis

A. stratified squamous epithelium (replenished ~25-45 days)

B. Five layers (From top to bottom)

1. Stratum corneum (Horny layer) “cornu” Greek for horn

a. Top layer and fully keratinized

b. 20-30 layers thick

c. Protect skin from abrasion and penetration

d. Glycolipids provide waterproofing

e. 40 lbs shed in a lifetime

f. Too far from blood vessels for diffusion so cells die

2. Stratum granulosum (Granular layer)

a. 3-5 cell layers thick

b. Keratinocytes produce keratin and squamous cells flatten as they are pushed upward (Held together by numerous desmosomes)

3. Stratum spinosum (Prickly Layer)

a. Prickly layer (Keratinocytes shrink but desmosomes hold in place)

b. Melanin granules (UV protection) and Langerhan’s (macrophage) cells abundant in this layer

4. Stratum basale (Base germinating layer)

a. Deepest layer of the epidermis

b. Single layer thick

c. Contain melanocytes and Merkel cells (Fine touch receptors)

5. Stratum lucidum (Clear layer)

a. Found only in thick skin between the Stratum granulosum and Stratum corneum

1. Palms of hands

2. Fingertips

3. Soles of feet

b. Only a few cell layers thick

IV. Dermis

A. Strong flexible connective tissue (collagen, elastin, and reticular fibers)

B. Papillae from upper dermis form ridges in the epidermis for grip (Fingerprints/footprints) 20% of thickness

C. Reticular layer of lower dermis 80% of thickness made up of dense irregular connective tissue

D. Pigments which affect skin color

a. Melanin (melan is Greek for black) (ONLY PIGMENT PRODUCED IN THE SKIN – varies in color from yellow to brown to black)

b. Carotene (Yellow/orange pigment found in plants which accumulates in the thick epidermis…this is why the soles of your feet appear orange)

c. Hemoglobin (Red from the red blood cells)

1. Cyanosis – bluish hue to the skin due to heart failure or respiratory distress

2. Erythema – reddish hue to the skin due to blushing, fever, hypertension, polycythemia

3. Pallor or blanching – pale skin hue due to emotional stress (fear, anger), anemia, or hypotension

4. Jaundice – yellow hue to the skin due to liver disorder

5. Bronzing of the skin due to Addison’s disease (adrenal cortex of the kidney hypofunctions)

6. Hematoma – (Bruises) blood leaks out of capillaries due to trauma and clots under the skin

E. Dermal structures

a. Sudoriferous (sweat) glands ( 2.5 million per person) 2 types:

1. Eccrine – Most abundant sweat gland covers most of the body

a. sweat is secreted by exocytosis into pores which empty onto the skin (500 mL per day… up to 12 L per day)

b. 99% water, remaining solutes are sodium chloride, vitamin C, urea, uric acid, ammonia, and lactic acid (which attracts mosquitoes)

c. Hot sweat begins on forehead and spreads to other parts of the body

d. Cold sweat due to fright or nervousness begins on palms, soles, and axillae (armpits) and spreads to other parts of the body

2. Appocrine - Located in the axillary and anogenital areas

a. Secreted into hair follicles beginning at puberty

b. Contains true sweat, lipids, and proteins and appears

viscous with a white/yellow hue

c. odorless upon secretion, but bacteria decompose molecules forming body odor

d. Increase of secretions during pain, stress, or sex but physiological function is unknown (believed to be sexual scent glands as menstruation affects output

e. Ceruminous glands are modified apocrine glands found in the external ear canal which secrete cerumen or ear wax which deters insects and blocks entry of foreign material

f. Mammary glands are modified apocrine glands which secrete milk

b. Sebaceous (Oil) glands

1. Located all over body except palms and soles

2. Secrete sebum which lubricates and softens hair and skin, prevents water loss, and has bactericidal properties

3. Whitehead - occurs when duct is blocked by accumulated sebum and staphylococcus infection begins

4. Blackhead – when whitehead oxidizes and dries out

c. Hair

1. Body hair – main function is to detect insects before they bite or sting

2. Found all over body except palms, soles, lips, nipples, and genitalia

3. Hair on the scalp prevents heat loss, UV protection, and protects against trauma

4. Eyelashes shield eyes from foreign particles

5. Nose hair filters air entering respiratory passages

6. Hair appearance due to shaft shape (Flat shaft = curly hair, oval shaft = wavy hair, round shaft = straight hair)

7. Hair color due to melanin (blonde to black hair) gray hair is a result of lack of melanin or the replacement of melanin with air bubbles in the hair shaft

8. Hair growth controlled by androgens (testosterone) in males and females (Hirsuitism due to ovarian or adrenal tumor)

9. Average hair growth is 2 mm per week

10. Hair thinning or baldness (alopecia) due to new growth hairs being outnumbered by hairs falling out (~100 per day)

d. Hair follicle

1. Extend from epidermis into the dermis

2. Form hair bulb and root plexus (Nerves surrounding the bulb) rub your arm hair gently…tickle you feel due to these nerves

3. Arrector pili muscles attach to hair and epidermis (stratum basale) and cause Goosebumps upon contraction

a. Trap air close to skin for warmth

b. Make us appear larger to predators

e. Nerves

1. Meissner’s corpuscles – light touch

2. Merkel’s disks – light touch

3. Pacinian corpuscles – deep pressure

4. Ruffini’s corpuscles – deep pressure and stretch

5. Bare nerve endings – pain, heat, cold

f. Nails

1. Analogous to hooves or claws of other animals

2. Nail matrix responsible for growth of new nail pushing nail distally

V. Pathophysiology

A. Skin Cancer

a. Benign (Non-spreading) vs. malignant (spread into other tissue)

b. Basal cell carcinoma – most common and least malignant

1. Shiny lesions in the stratum basale which grow into the dermis

2. 99% cure rate after surgery

c. Squamous cell carcinoma

1. Cells of the stratum spinosum form a lesion which appears small red and round

2. Lesion usually forms on scalp, ears, lips, or hands

3. Grows rapidly and can metastasize if not removed

4. If caught early and removed, chance of cure is good

d. Melanoma (5% of skin cancers)

1. Cancer of the melanocytes

2. Most dangerous of the skin cancers

3. Appears as a brown or black spreading patch

4. Metastasizes rapidly to lymph and blood

5. ABCDE rule to detect

a. Asymmetry – two sides don’t match

b. Border irregularity – not smooth and have indentations

c. Color – more than one color

d. Diameter – larger than 6 mm in diameter

e. Elevation – elevated above skin surface

B. Burns

a. 1st degree – only epidermal damage e.g. sunburn

1. Heal in 2-3 days

b. 2nd degree – epidermis and upper dermis damaged

1. Blisters form (Fluid collects between dermis and epidermis)

2. Heal in 3-4 weeks

3. Critical if more than 25% of the body is affected

c. 3rd degree – epidermis and all of dermis is damaged

1. Charring of muscle is common

2. Nerve endings are destroyed so not painful

3. Fluid loss can be catastrophic (dehydration & electrolyte imbalance lead to renal failure and shock)

4. Infection can be rampant

5. Skin grafting necessary

6. Critical if more than 10% of the body is affected or if the face, hands, or feet have 3rd degree burns

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